Microstructured waveguide illuminator

ABSTRACT

In one aspect, there is provided an apparatus. The apparatus may include a waveguide layer to guide an optical beam, and a lenslet layer, coupled to a surface of the waveguide layer, to focus a portion of the optical beam. The apparatus may further include a first active layer, coupled to another surface of the waveguide layer, to allow the portion of the optical beam to decouple from the waveguide layer by passing through the first active layer in at least one selectable region of the first active layer. The apparatus may further include a redirecting layer, coupled to or proximate to the first active layer, to redirect the portion of the optical beam decoupled from the waveguide towards the lenslet layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/883,000, entitled “MICROSTRUCTURED WAVEGUIDE ILLUMINATOR”,filed on Sep. 26, 2013, the contents of which is incorporated byreference in its entirety herewith.

TECHNICAL FIELD

The subject matter disclosed herein relates to sources of lighting and,in particular, light-emitting diode sources with adjustabledirectionality for general lighting and for display backlighting.

BACKGROUND

Light emitting diodes (LEDs) are considered by many to have superiorelectrical to optical energy conversion efficiency as well as longerlifetimes compared to conventional lighting devices such as fluorescentlights and incandescent lights. Conventional lighting devices aredesigned to either provide directional illumination or diffuseillumination, but once designed and manufactured, conventional lightingcannot switch between directional and diffuse illumination. Moreover,the direction of the illumination cannot be internally adjusted.

SUMMARY

In one aspect, there is provided an apparatus. The apparatus may includea waveguide layer to guide an optical beam, and a lenslet layer, coupledto a surface of the waveguide layer, to focus a portion of the opticalbeam. The apparatus may further include a first active layer, coupled toanother surface of the waveguide layer, to allow the portion of theoptical beam to decouple from the waveguide layer by passing through thefirst active layer in at least one selectable region of the first activelayer. The apparatus may further include a redirecting layer, coupled toor proximate to the first active layer, to redirect the portion of theoptical beam decoupled from the waveguide towards the lenslet layer.

In some variations, one or more of the features disclosed hereinincluding the following features can optionally be included in anyfeasible combination. The apparatus may include a second active layer toselect an intensity of the portion of the optical beam decoupled fromthe waveguide layer. The second active layer may further select a colorfrom a color filter array for the portion of the optical beam decoupledfrom the waveguide layer. The redirected portion of the optical beamdecoupled from the waveguide layer may be steered in a predetermineddirection by adjusting the selectable regions of the first active layer.One or more of the first active layer and the second active layer maycomprise a liquid crystal material. The redirecting layer may compriseprism decouplers. The lenslet layer may comprise a plurality of lensesconfigured in an array. The optical beam may propagate in a directionthat is substantially parallel to the waveguide, the first active layer,the second active layer, the redirecting layer, and the lenslet layer.The apparatus may be configured as a display and may include a facetracker to determine at least a direction from one of the plurality oflenses to an eye of a user.

The above-noted aspects and features may be implemented in systems,apparatuses, methods, and/or computer-readable media depending on thedesired configuration. The details of one or more variations of thesubject matter described herein are set forth in the accompanyingdrawings and the description below. Features and advantages of thesubject matter described herein will be apparent from the descriptionand drawings, and from the claims. In some exemplary implementations,one of more variations may be made as well as described in the detaileddescription below and/or as described in the following features.

DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, show certain aspects of the subject matterdisclosed herein and, together with the description, help explain someof the principles associated with the subject matter disclosed herein.In the drawings,

FIG. 1 depicts an example of an apparatus for collimating light from adiffuse source that redirects portions of the beam to provide couplingto a thin planar waveguide, in accordance with some exampleimplementations;

FIG. 2 depicts an example of an apparatus for redirecting portions of abeam using reflective facets to provide coupling to a thin planarwaveguide, in accordance with some example implementations;

FIG. 3 depicts a waveguide with periodic features to scatter light fromthe waveguide, in accordance with some example implementations;

FIG. 4 depicts lenslet sheet and waveguide sheet, in accordance withsome example implementations;

FIG. 5 depicts a lenslet array and the effects of translating androtating the lenslet array, in accordance with some exampleimplementations;

FIG. 6 depicts a resulting beam shape and beam direction as a functionof lenslet translation and rotation, in accordance with some exampleimplementations;

FIG. 7 depicts a beam steering angle and crosstalk as a function oflenslet displacement, in accordance with some example implementations;

FIG. 8 depicts three spatial light modulators, in accordance with someexample implementations;

FIG. 9 depicts an apparatus including an active material to steer a beamin a flat panel display providing a controllable viewing direction, inaccordance with some example implementations;

FIG. 10 depicts an example implementation of FIG. 9 providingstereoscopic display to a viewer; and

FIG. 11 depicts an apparatus including a first active material toprovide a controllable viewing direction, and a second active materialto provide color and intensity to output light of a flat panel display,in accordance with some example implementations.

Like labels are used to refer to same or similar items in the drawings.

DETAILED DESCRIPTION

Methods and apparatuses are disclosed including waveguides andmicro-optic structures for backlights that controllably route light fromone or more small area bright sources to evenly illuminate the surfaceof a large panel. The methods and apparatuses may be used to makeinexpensive light-emitting diode (LED) light fixtures for officelighting. The light fixtures may be electrically or mechanicallycontrolled to adjust the direction and divergence of the emitted light.In some example implementations, the direction of light emitted fromregions of a liquid crystal display may be controlled in real-time.Real-time control may provide energy efficiency, viewing privacy, and/ora multi-user three-dimensional display, without the use of specialglasses.

In accordance with some example implementations, an apparatus and methodto provide lighting from a planar surface is disclosed. The angle of thelighting from the surface may be controlled. In some exampleimplementations, the angle may be fixed by design of a waveguide sheet.In some example implementations, the angle may be continuouslyadjustable by mechanical positioning of a lenslet array or by electroniccontrol of an active material, such as a liquid crystal material.

The fixed or adjustable beam angle may be controlled by periodicmicro-optic structures in a waveguide and by lenslets. The direction ofthe light emission may be controlled by the position of the micro-opticmicrostructures (e.g., also referred to as “extraction” structures)relative to a periodic array of lenslets. The lenslets may be separatefrom the waveguide. The emission direction of a fixed beam apparatus maybe determined by the physical shape of the lenslets and the shape andrelative position of the waveguide light extraction structures. Theposition of the lenslets relative to the waveguide extraction features,and so the direction of light emission, may be controlled by moving thelenslet array relative to the waveguide.

The lenslet array may be used to direct the light into a predeterminedpattern, where the position and size of the output facets (or theposition and focal length of the lenslets) determines the direction ofemission for each region of the overall device surface. In this way, thedirection of emission and divergence angle a planar LED light fixturemay be controlled. The control may be mechanical, for example by using apair or knobs or screws, or it may be electro-mechanical, for example byusing a motor.

In some implementations, each element of an extraction microstructurearray is electrically controlled. For example, a liquid crystal panel inproximity to a waveguide may be electrically controlled such that therefractive index of localized regions of the liquid crystal panel have arefractive index that is different from other regions of the liquidcrystal panel. The difference in the index of refraction at theinterface between the waveguide and the surrounding volume determinesthe reflection at that interface, and so the difference in the index ofrefraction at the interface controls the light emission from that regionof the waveguide. Light emitted from the waveguide may be directed by afixed array of refractive features or a fixed array of reflectivefeatures. These features act to direct the emitted light into adirection determined by the specific area of emission from thewaveguide.

By controlling the refractive index of regions of the liquid crystalpanel, the liquid crystal panel may determine the resulting beam anglein real-time. In this way, a liquid crystal display may be produced thatprovides a visual display that is only visible in a particulardirection. The display may not be viewed from other directions. In someimplementations, controlling the viewing angle provides privacy to aviewer. Controlling the viewing angle also reduces the energy requiredfor the display. In some implementations, controlling the viewing anglemay be used to provide different images to each of the two eyes of aviewer to enable a three-dimensional display.

A face-tracker and/or eye-tracker may be used to track the positions ofa viewer's face and/or eyes to enable viewing as the viewer and/ordisplay moves. The face-tracker or eye-tracker may be implemented usinga camera mounted near the display. A face-tracker may performface-recognition to locate the viewer's head. An eye-tracker may locateone or both of the viewer's eyes. The location of the viewer's headand/or eyes may be used to adjust properties of the display. Propertiesof the display that may be controlled include the divergence angle ofthe light from the display and the total illuminating power of thelight. These properties may be adjusted to reduce the energy consumptionof the display and/or limit access to particular viewing angles(viewers). The viewing angle and intensity may be adjusted in real-time,in response to the number and location of viewers.

FIG. 1 depicts an illumination device 100 that provides a planar lightoutput in accordance with some implementations. The illumination devicemay expand and partially collimate the light with a collimator 110 froma diffuse source, such as a light emitting diode 120 (labeled “LEDsource”). Waveguide in the illumination device may “peel off” segmentsof a rectangular aperture 130, re-arranging the segments 140 to bearranged to produce an extended planar light source. Diagram 150 showsan example relationship between a source divergence angle and opticalcoupling efficiency, in accordance with some implementations. Theoptical coupling efficiency is the ratio of the energy of the lightsource to the total light energy coupled into confined modes of thewaveguide.

FIG. 2 depicts illumination devices 210, 220, and 230 that provide aplanar light output in accordance with some implementations. Light froma collimator, such as collimator 110, enters at 205A-C into illuminationdevice 210, 220, and 230. Reflective facets each redirect a portion ofthe light from the collimator to planar waveguide segments 140 arrangedto produce an extended planar light source. Diagram 240 shows an examplerelationship between a source divergence angle and the efficiency, inaccordance with some implementations.

FIG. 3 depicts examples of waveguides with periodic features to scatterlight in a waveguide. At 310, a waveguide is shown with periodicscattering structures. At 320, a waveguide is shown with periodicreflective surfaces. At 330, a waveguide is shown with a stepped lightguide structure.

At 310, a waveguide is shown with periodic scattering structures312A-312D. Light may be scattered from each scatterer 312A-312D(scattering from only scatterer 312C is shown). Light may be reflectedfrom the right-side wall 316 back to the source at the left-side wall314. In some implementations, no reflection occurs at the rightside-wall 316. In these implementations, the spacing between scatterers312A-312D may vary based on the distance that the scatterer is from thesource 314. For example, as the distance between the source and thescatterer increases, the incremental distance to the next scatterer maydecrease (or increase). At 310, equal spacing between scatterers312A-312D is shown. At 310, four scatterers are shown but any othernumber of scatterers may used as well.

At 320, periodic reflective surfaces 322A-322F which may be mirrored orreflect due to total internal reflection, redirect light in thewaveguide (reflection from only reflector 322C is shown). The waveguidecross section may decrease with each ejection site. The opticalintensity remains constant throughout the waveguide while the modalvolume decreases as a function of propagation distance. Ejection of allthe light entering the waveguide may occur in a single pass. Forexample, all the light or nearly all the light entering at 314 may bereflected by one of the reflective surfaces 322A-322F.

At 330, a stepped light guide uniformly redirects light to individualejection sites 332A-332E (light reflected from each ejection site332A-332E is shown). Light may makes one pass through the structurebefore being ejected by a facet. For example, all the light or nearlyall the light entering at 314 may be ejected by one of the ejectionsites 332A-332E. Each ejection site may subtend the entire thickness ofthe light guide 330.

FIG. 4 depicts a lenslet sheet 410 and waveguide sheet 420, inaccordance with some implementations. Light may be injected into thewaveguide sheet 420 from the edges 430, the top surface 434, and/or thebottom surface 432 by injection structures that limit the angularspectrum of the injected light. For example, light injected from theleft edge may be shown in FIG. 4. The waveguide sheet 420 may bebordered by air or a low refractive index cladding to permit light to beguided by total internal reflection (TIR). As light travels in thewaveguide sheet 420, light interacts with small prism decouplers 440,which decouple the guided light into a narrow range of angles travellingperpendicular to the waveguide. The decoupled light may interact withthe lenslet sheet 410 which is comprised of an array of refractive orreflective lenslets. The interaction of the source with a particularprism decoupler and lenslet is shown in 400.

FIG. 5 depicts steering a beam generated from a waveguide sheet 420,prism decouplers 440, and a lenslet sheet 410 (or lenslet array). Thedirection and divergence of the emitted light is regulated bymechanically or electrically controlling the positions of the prismdecouplers 440 relative to the lenslet sheet 410 is detailed below.

In FIG. 5, light from an extended Lambertian source (e.g., LED) may beconditioned by an injection structure for efficient coupling into planarlight guide 420. The injection structure may limit the angular extent ofthe injected light not only to ensure total internal reflection (TIR)confinement in the waveguide 420, but also so a reduced angular extentcan be leveraged during beam steering.

The waveguide 420 may direct the injected light to an ejection featuresuch as prism decoupler 440, where light is decoupled. Depending on thetype of ejection feature, the angular extent of the light may or may notbe altered. The spatial extent of the ejection features may be smallrelative to the lenslet aperture to limit divergence.

The ejected light may be directed to a lens in a lenslet sheet 410 whosefocal plane is roughly at a corresponding ejection feature such as prismdecoupler 440. In some implementations, the lens substantiallycollimates the light scattered from the ejection feature and directs thelight in a particular direction. Light is steered by the lens dependingon the radial offset between the optical axis of the lens and theejection feature.

Partial illumination of the lens aperture may reduce aberrations andcrosstalk between adjacent lenses. This may require the lightpropagating in the light guide to have a limited divergence and for theejection features to maintain that divergence. Lower f-number lenses mayenable a larger steering angle as well as lower crosstalk betweenadjacent lenslets.

At 510, a two-by-two lenslet array 510 is aligned with a two-by-twoejector array 540 so that the four beams from the four lenses in thelenslet array 510 are collimated. The combination of the four beams isalso a collimated beam. At 520, translation of lenslet array 510relative to ejector array 540 enables steering of each of the four beamsin the same direction. At 530, rotation of lenslet array 510 relative toejector array 540 controls overall beam divergence by steering the fourbeams in different directions.

FIG. 6 depicts a diagram 600 showing the effect of translating and/orrotating a lenslet array, in accordance with some implementations. Thevertical axis labeled “collimated” shows the effect of translating thelenslet array with respect to the ejection features of FIG. 4,reflection points/surfaces of FIGS. 3 and 6, and/or scattering points ofFIG. 3. Steering of the individual beams and thus the collection ofbeams is in the same direction. The amount of steering off boresight isdependent on the amount of translation. The horizontal axis shows theeffect of rotating the lenslet array with respect to the decouplers ofFIG. 4, reflection points/surfaces of FIGS. 3 and 6, and/or scatteringpoints of FIG. 3. Rotation of the lenslet array may cause differentbeams in the collection of beams to be steered in different directionsso that the collection of beams diverges. The amount of divergence maydepend on the amount of rotation.

FIG. 7 at 700 depicts the luminous intensity of a beam steered bytranslation of the lenslet array and the crosstalk between lenslets inthe array, in accordance with some implementations. As the lenslet arraytranslation (e.g., “offset”) increases, the steered angle from boresightincreases. As the offset increases, the crosstalk also increases.

FIG. 8 depicts two spatial light modulators 810 and 820 in accordancewith some implementations. The spatial light modulators 810, 820, and830 may include variable index medium (e.g. liquid crystal material).Other variable index material may be used as well.

In some implementations consistent with FIG. 8 at 810, a change inrefractive index in a material 814 (e.g., liquid crystal material)adjacent to a waveguide 812 may cause ejection of light from thewaveguide. For example, reflection of light (or light ejection) may becaused by the refractive index of the liquid crystal being differentfrom the adjacent waveguide material. One of the locations 816 with adifferent refractive index along the length of the waveguide is shown in810. In other areas shown at 810, the refractive index of the liquidcrystal material may be the same or very similar to the refractive indexof the waveguide material. The change in refractive index of the liquidcrystal material may be caused by applying a voltage across the materialvia electrodes.

In some implementations consistent with FIG. 8 at 820, the refractiveindex of a material adjacent to waveguide 822 such as liquid crystal 824may be different from the refractive index of waveguide material 822.Light may be confined to the waveguide 822 except at locations where therefractive index of the liquid crystal 824 has been changed to be equalor nearly equal to the refractive index of the waveguide 822 material.At locations such as 826 where the refractive index is changed to beingequal or nearly equal to the waveguide material, light may propagate outof waveguide 822 and into the liquid crystal material 824 to redirectivesurfaces such as surface 828 that may cause reflection (or lightejection) from the waveguide 822. The redirective surfaces may includemetalized surfaces, surfaces with refractive index such that totalinternal reflection occurs, or reflective coatings.

In some implementations consistent with FIG. 8 at 830, the refractiveindex of a material adjacent to waveguide 822 such as liquid crystal 832may be different from the refractive index of the waveguide material822. Light may be confined to the waveguide 822 except at locationswhere the refractive index of the liquid crystal 832 has been changed tobe equal or nearly equal to the refractive index of the waveguide 822material. At these locations where the refractive index of liquidcrystal material 832 may be changed to being equal or nearly equal tothe waveguide 822 material, light may propagate out of the waveguide822, through the liquid crystal material 832 and transparent electrodes834 to one or more sheets of prisms 836 which may change thedirectionality of the light propagating out of the waveguide 822. Forexample, the light propagating out of the waveguide may be substantiallyperpendicular to the waveguide. The prisms may include refractiveprisms, metalized surfaces, or reflective coatings.

FIG. 9 at 900 depicts an optical beam 908 propagating in a waveguide904. Coupled to the top surface of the waveguide is lens 902 from alenslet array. Coupled to the bottom surface of the waveguide is activelayer 824. Under active layer 824 may be a decoupling sheet 930.

When a portion of the light from beam 908 reaches active layer 824, aportion of the beam is reflected back into the waveguide 822 and aportion passes through the active layer at 910. In some exampleimplementations, active layer 824 may include materials including liquidcrystal materials or other materials that change reflectivity,reflection coefficient, or refractive index via a bias voltage acrossthe material. For example, by controlling the reflection coefficient ofregions of active layer 824 such as active region 910, light may beallowed to pass through active layer 824 in that region and impinge on adecoupling sheet 930. Decoupling sheet 930 may cause the direction ofpropagation of the light impinging on decoupling sheet 930 to change toa direction that allows the light to pass towards lens 902 at 912. Bycontrolling the reflection coefficient of regions of the active layer824 that are small compared to the size of the lens, the location of theeffective decoupling feature relative to the lens may be controlled. Insome implementations, controlling the position of active region 910 mayallow for control of the direction of the outgoing light 914 from lens902.

In implementations consistent with some displays (e.g., computermonitors, televisions, and so on), an active material (e.g., liquidcrystal such as 814 and 824) may separate a waveguide layer (e.g., 812,822) from a decoupling sheet (e.g., 930). The active material may bedivided into individually controllable regions which are each smallerthan the area of a single lenslet as detailed with respect to FIG. 9.The transmission/reflection of each region may be set electrically tocontrol the local degree of interaction of guided light with thedecoupling sheet. In this way, the position of the effective decouplingfeature relative to the lenslet may be controlled for each lenslet. Theintensity and direction of emitted light can be tuned for each lensletand modulated at a frequency dependent on the response time of theactive material.

An apparatus consistent with FIG. 9 may be used in a flat panel displayto provide a controllable viewing direction when active materials withresponse times as fast or faster than video frame rates are used. For agiven viewing angle and distance, the appropriate lenslet f-number, asmall enough sub-pixel pitch, and information about the viewer'slocation, the system may couple light directly into the viewer's eyes.In some example implementations, light may be independently coupled intoeach eye of the viewer. In this way, a stereoscopic display may beproduced. Each lenslet may convey one pixel, or a localized region ofpixels, of the image to each eye. High electrical and opticalefficiencies may be achieved compared to conventional displays, becausethe emitted light is selectively directed straight into the viewer'seyes, as opposed to being emitted in a large solid angle. Theselectively aimed light may also make displayed images private to theviewer. In some example implementations, the system may support aiminglight to multiple viewers by tracking the locations of each viewer'seyes simultaneously.

FIG. 10 depicts an example implementation of FIG. 9 providingstereoscopic display to a viewer.

FIG. 11 at 1100 depicts an apparatus including a first active materialto provide a controllable viewing direction, and a second activematerial to provide color and intensity to output light of a flat paneldisplay, in accordance with some example implementations.

At 1100, an optical beam 908 may propagate in a waveguide 904. Coupledto the top surface of the waveguide may be a first liquid crystal layer824. Coupled to the top surface of the first liquid crystal layer 824may be a prism sheet 930. Coupled to the top of the prism sheet layer930 may be a second liquid crystal layer 1120. Coupled to the topsurface of the second liquid crystal layer 1120 may be a color filterarray 1110. Coupled to the top surface of color filter array 1110 may bea lenslet sheet or array 410. Instead of being coupled to thecorresponding adjacent layer(s), one or more of the layers in FIG. 11may be proximate to the corresponding adjacent layer(s). FIG. 11 alsorefers to FIGS. 4, 8, 9, and 10.

When a portion of the light from beam 908 reaches first liquid crystallayer 824 (also referred to as an active layer), a portion of the beammay be reflected back into the waveguide 822, and a portion of the beammay pass through the first liquid crystal layer at 910A and 910B. Bycontrolling the reflection coefficient of regions 910A and 910B of firstliquid crystal layer 824, light may be allowed to pass through activelayer 824 at 910A and 910B and impinge on a prism sheet 930 (alsoreferred to as a decoupling sheet). Prism sheet 930 may cause thedirection of propagation of the light impinging on prism sheet 930 tochange to a direction that allows the light to pass towards secondliquid crystal layer 1120. Although FIG. 11 appears to show the lightpassing through liquid crystal sheet 824 changing direction at theliquid crystal sheet 824, the light changes direction at the prism sheet930. By controlling the reflection coefficient of regions of the secondliquid crystal layer 1120 that are small compared to the size of regions910A and 910B, and thus the light passing through 910A and 910B, thelocations where color filter array 1110 are illuminated may be selected.Color filter array 1110 may include a pattern of regions of differentcolors. By illuminating specific locations of color filter array 1110,the color of the light directed towards lenslet array 410 may becontrolled.

An apparatus consistent with FIG. 11 may be used to provide a color flatpanel display with a controllable viewing direction. Each lenslet in 410may convey one color pixel, or a localized region of color pixels, ofthe image to each eye.

In accordance with some implementations, an apparatus comprises: awaveguide layer to guide an optical beam; a lenslet layer, coupled to asurface of the waveguide layer, to focus a portion of the optical beamdecoupled from the waveguide layer; a first active layer, coupled toanother surface of the waveguide layer, to allow the portion of theoptical beam to decouple from the waveguide layer by passing through thefirst active layer in at least one selectable region of the first activelayer; a redirecting layer, coupled to or proximate to the first activelayer, to redirect the portion of the optical beam decoupled from thewaveguide towards the lenslet layer; and a second active layer andcorresponding color filter array to provide color selection andintensity control of the portion of the optical beam decoupled from thewaveguide layer.

The subject matter described herein may be embodied in systems,apparatus, methods, and/or articles depending on the desiredconfiguration. For example, apparatuses and/or processes describedherein can be implemented using one or more of the following: aprocessor executing program code, an application-specific integratedcircuit (ASIC), a digital signal processor (DSP), an embedded processor,a field programmable gate array (FPGA), and/or combinations thereof.These various implementations may include implementation in one or morecomputer programs that are executable and/or interpretable on aprogrammable system including at least one programmable processor, whichmay be special or general purpose, coupled to receive data andinstructions from, and to transmit data and instructions to, a storagesystem, at least one input device, and at least one output device. Thesecomputer programs (also known as programs, software, softwareapplications, applications, components, program code, or code) includemachine instructions for a programmable processor, and may beimplemented in a high-level procedural and/or object-orientedprogramming language, and/or in assembly/machine language. As usedherein, the term “machine-readable medium” refers to any computerprogram product, computer-readable medium, computer-readable storagemedium, apparatus and/or device (e.g., magnetic discs, optical disks,memory, Programmable Logic Devices (PLDs)) used to provide machineinstructions and/or data to a programmable processor, including amachine-readable medium that receives machine instructions. Similarly,systems are also described herein that may include a processor and amemory coupled to the processor. The memory may include one or moreprograms that cause the processor to perform one or more of theoperations described herein. For example, the control aspects of thelight sources or display such as a liquid crystal display may includenon-transitory computer-readable medium including computer program codefor the control. Moreover, the design or optimization of the design ofthe light sources or liquid crystal display may include non-transitorycomputer-readable medium including computer program code for the designor optimization.

Although a few variations have been described in detail above, othermodifications or additions are possible. In particular, further featuresand/or variations may be provided in addition to those set forth herein.Moreover, the implementations described above may be directed to variouscombinations and subcombinations of the disclosed features and/orcombinations and subcombinations of several further features disclosedabove. In addition, the logic flow depicted in the accompanying figuresand/or described herein does not require the particular order shown, orsequential order, to achieve desirable results. Other implementationsmay be within the scope of the following claims. Furthermore, thespecific values provided in the foregoing are merely examples and mayvary in some implementations.

Although various aspects of the invention are set out in the claims,other aspects of the invention comprise other combinations of featuresfrom the described implementations with the features of the claims, andnot solely the combinations explicitly set out in the claims.

It is also noted herein that while the above describes exampleimplementations of the invention, these descriptions should not beviewed in a limiting sense. Rather, there are several variations andmodifications that may be made without departing from the scope of thepresent invention as defined in the appended claims.

1. An apparatus comprising: a waveguide layer to guide an optical beam;a lenslet layer, coupled to a surface of the waveguide layer, to focus aportion of the optical beam; a first active layer, coupled to anothersurface of the waveguide layer, to allow the portion of the optical beamto decouple from the waveguide layer by passing through the first activelayer in at least one selectable region of the first active layer; and aredirecting layer, coupled to or proximate to the first active layer, toredirect the portion of the optical beam decoupled from the waveguidetowards the lenslet layer.
 2. The apparatus of claim 1, furthercomprising: a second active layer to select an intensity of the portionof the optical beam decoupled from the waveguide layer.
 3. The apparatusof claim 2, wherein the second active layer further selects a color froma color filter array for the portion of the optical beam decoupled fromthe waveguide layer.
 4. The apparatus of claim 1, wherein the redirectedportion of the optical beam decoupled from the waveguide layer issteered in a predetermined direction by adjusting the at least oneselectable region of the first active layer.
 5. The apparatus of claim2, wherein one or more of the first active layer and the second activelayer comprises a liquid crystal material.
 6. The apparatus of claim 1,wherein the redirecting layer comprises prism decouplers.
 7. Theapparatus of claim 1, wherein the lenslet layer comprises a plurality oflenses configured in an array.
 8. The apparatus of claim 2, wherein theoptical beam propagates in a direction that is substantially parallel tothe waveguide, the first active layer, the second active layer, theredirecting layer, and the lenslet layer.
 9. The apparatus of claim 7,further comprising: a face tracker to determine at least a directionfrom one of the plurality of lenses to an eye of a user, wherein theapparatus is configured as a display.
 10. A method comprising: guiding,by a waveguide layer, an optical beam; focusing, by a lenslet layercoupled to a surface of the waveguide layer, a portion of the opticalbeam; allowing, by a first active layer coupled to another surface ofthe waveguide layer, the portion of the optical beam to decouple fromthe waveguide layer by passing through the first active layer in atleast one selectable region of the first active layer; and redirecting,by a redirecting layer coupled to or proximate to the first activelayer, the portion of the optical beam decoupled from the waveguidetowards the lenslet layer.
 11. The method of claim 10, furthercomprising: a second active layer to select an intensity of the portionof the optical beam decoupled from the waveguide layer.
 12. The methodof claim 11, wherein the second active layer further selects a colorfrom a color filter array for the portion of the optical beam decoupledfrom the waveguide layer.
 13. The method of claim 10, wherein theredirected portion of the optical beam decoupled from the waveguidelayer is steered in a predetermined direction by adjusting the at lastone selectable region of the first active layer.
 14. The method of claim11, wherein one or more of the first active layer and the second activelayer comprises a liquid crystal material.
 15. The method of claim 10,wherein the redirecting layer comprises prism decouplers.
 16. The methodof claim 10, wherein the lenslet layer comprises a plurality of lensesconfigured in an array.
 17. The method of claim 14, wherein the opticalbeam propagates in a direction that is substantially parallel to thewaveguide, the first active layer, the second active layer, theredirecting layer, and the lenslet layer.
 18. The method of claim 16,further comprising: tracking, by a face tracker, a face of a user todetermine at least a direction from one of the plurality of lenses to aneye of the user, wherein the guiding, the focusing, the allowing, theredirecting, and the tracking are configured to provide a display.
 19. Anon-transitory computer-readable medium encoded with instructions that,when executed by at least one processor, cause operations comprising:guiding, by a waveguide layer, an optical beam; focusing, by a lensletlayer coupled to a surface of the waveguide layer, a portion of theoptical beam; allowing, by a first active layer coupled to anothersurface of the waveguide layer, the portion of the optical beam todecouple from the waveguide layer by passing through the first activelayer in at least one selectable region of the first active layer; andredirecting, by a redirecting layer coupled to or proximate to the firstactive layer, the portion of the optical beam decoupled from thewaveguide towards the lenslet layer.
 20. The non-transitorycomputer-readable medium of claim 19, further comprising: a secondactive layer to select an intensity of the portion of the optical beamdecoupled from the waveguide layer. 21.-28. (canceled)